The present invention generally relates to the separation of gas from liquid, particularly with respect to applications pertaining to pulping and oxygen delignification.
Degassing unit operations are known. For example, a conventional degasser is illustrated in FIGS. 1A and 1B. FIG. 1B shows a cross-sectional view (1B-1B) of the process shown in FIG. 1A, and like items are identified with like numerals. The system 100 includes input stream 104, and output streams 124 and 136. Input stream 104 may include liquids and gasses. The liquids may comprise primarily water, and the gasses may include process waste gasses, such as carbon dioxide, carbon monoxide, oxygen, methane, etc. The system 100 separates these gases, which may exit primarily via output stream 124.
In FIGS. 1A and 1B, input stream 104 flows through conduit 110 to pump 112, which is connected to shaft 114 and motor 116. As shaft 114 rotates, the liquid-gas mixture is pumped through conduit 118 to the degasser 102. Conduits 110 and 118 may be flexible hoses. As illustrated, conduit 118 is connected to inlet pipe 120. Inlet pipe 120 is connected to a pipe 122 at the top of degasser 102. As the liquid-gas mixture enters the pipe 122, the liquids tend to fall, while the gasses tend to rise and exit out of the top of the degasser 102 through output stream 124 to a gas collector (not shown).
As shown by the arrows at the base of pipe 122, the liquid flows up the approximately cylindrical tank defined by base 128 and walls 126. The liquid exits through conduit 134 to output stream 136, which is sent to liquid waste.
At the base of the tank, there is a flushing connection 130. As solids (e.g., pulp, etc.) accumulate at the base of the degasser, there is a potential for clogging. Those solids are generally manually removed periodically using the flushing connection 130. As illustrated base 128 is roughly parallel with the ground, such that the walls 126 intersect base 128 perpendicularly.
For applications involving low amounts of solids in the liquid-gas stream, the prior art may be suitable. That is, the periodic, manual cleaning may work well because a low-solids content will generally require a relatively long period of time before cleaning becomes necessary.
But in applications having a larger (or non-insignificant) amount of solids (such as pulp, etc.) in the liquid-gas stream to be separated into gas and liquid, there may be a need for a degasser that does not clog, is easy to clean or purge (or automatically cleaning), and disposes of waste.
In one aspect, certain embodiments of the present invention generally relate to a degasser having a flapper opening including a hinge and a counterweight. The hinge and counterweight may permit purging of any liquids and solids without regular human intervention. In other embodiments, there is a fixed opening at the base of the degasser, such that there is a constant emptying from the bottom of the tank.
In another aspect, certain embodiments of the present invention generally relate to an inlet design that facilitates separation of any solids (e.g., pulp, etc.) by reducing the velocity of the inlet stream on entry into the degasser. For example, this may be done using a flange. Facilitating the separation of solids may prevent clogging.
In one respect, certain embodiments of the present invention generally relate to a degasser for separating gas from liquid comprising: a substantially cylindrical tank comprising a top, a bottom, and a circumferential side wall; an inlet pipe for carrying a stream comprising a mixture of gas and liquid; and a vent pipe connected to the tank, wherein the vent pipe receives separated gas; wherein the bottom of the tank is connected to the circumferential side wall by a hinge such that the hinge at least partially opens when a sufficient mass of liquid weighs down on the bottom of the tank and at least partially closes when an insufficient mass of liquid weighs down on the bottom of the tank; and wherein the separated liquid exits the tank via an opening created as the hinge opens and creates a gap between the bottom of the tank and the circumferential side wall.
In one respect, certain embodiments of the present invention generally relate to a method of separating gas from liquid, the method comprising the steps of feeding a mixture of gas and liquid to a substantially cylindrical tank comprising a top, a bottom, and a circumferential side wall, wherein the bottom of the tank is connected to the circumferential side wall by a hinge that opens when a sufficient mass of liquid weighs down on the bottom of the tank and closes when an insufficient mass of liquid weighs down on the bottom of the tank; removing gas from the tank using a vent pipe attached to the top of the tank; and removing liquid from the tank using an opening created as the hinge opens and creates a gap between the bottom of the tank and the circumferential side wall.